Spark arrester



5 m, ,m .a JN m ve a 5?/ m, fr. Rw #M Eml mmm. WM .Ku HmA und SM m.. 8. 3 9 1 oo 1 LW d.. .......nu-lnu M, W 0 Mw/J Patented Oct. 18, 1938 UNITED STATES 2,133,506 SPARK ARRESTER Henry Giese, Ames, Iowa` Application August 9,

2 Claims.

My object is to provide a spark arrester which can be manufactured at a minimum cost and which has maximum efficiency in preventing the escape of sparks from chimneys.

More particularly it is my object to provide a spark arrester which has the proper relative selection, arrangement and proportioning of parts for making an efficient spark arrester.

With these and other objects in View, my invention consists in the construction, arrangement and combination of the various parts of my spark arrester, whereby the objects contemplated are attained, as hereinafter more fully set forth, pointed out in my claims and illustrated in the accompanying drawing, in

which:

Figure 1 is a perspective view of a spark arrester embodying my invention.

Figure 2 is a top or plan View of the same; and Figure 3 is a vertical sectional view of the I spark arrester taken on the line 3-3 of Figure 1.

It has been exceedingly difficult to provide a satisfactory spark arrester for chimneys of ordinary dwelling houses. Yet the need for a proper spark arrester is acute.

-In the State of Iowa sparks escaping from chimneys result in more fires of buildings than any other single cause. I have engaged in an extensive study of the spark arrester problem for a number of years just past. If householders usedY first class fuels and had noncombustible roofs, spark arresters might not be necessary. The facts however,` are as I have already stated the'm. There are many obstacles that stand in vthe way of the provision of a commercially prac- 4tical spark arrester and 'some of these will be mentioned in connection with the description given below. I

I might say in explanation of the difficulty of getting a commercially practical spark arrester that there are four means available which might be used to prevent the escape of sparks of such large size as might set fire to a roof.

They are: (1) the screening of the soot particles from the gas; (2) breaking up of the soot particles into sizes too small to cause ignition of an ordinary roof, particularly a shingle roof; (3) the abrupt changing of the direction of flow of the gas for thereby projecting. the soot particles out of the stream (as is done in automobile air cleaners); and (4) reducing the velocity of the air stream for thereby lowering its transporting power.

There have been many spark arresters designed to use the first expedient. Almost in- 1937, Serial No. 158,185

variably, however, when it is attempted to commercialize such product, it is found that the difficulty of clogging is encountered. In many instances the construction of the heating plant or of the chimney is faulty and is affected with v a faulty draft-in the chimney. Clogging makes it impossible to keep the spark arrester in place on the chimney.

It has been the practice to gradually increase the mesh to the point where the screeningv function was lost in the arrester, in order to allow draft in partially clogged arresters. Our extensive experiments vhave shown that the selection of the proper mesh will solve the problem in manyy cases but that ther'eare enough instances' of clogging to make it desirable to adopt some additional means for securing proper results.

'Io attempt to meet the problem by the first expedient mentioned is unsatisfactory because an arrester of that type interferes too much with the maintenance of proper draft. f

The second expedient is a good one but it is almost impossible to successfully break up all of the soot particles 'into pieces small enough to accomplish the desired object. v

'Ihe third expedient involves the problem of resistance which slows down thevelocity of the gas stream causing smoke and damage in the house. 5

I have found by longexperience that the best results are secured by a combination of all four of .the above expedients. Following tests determining vhow each of such expedients might be employed, I have come to the conclusion that a satisfactory arrester, perhaps the best for use on residences in this sectionof the country, is that which I shall now describe. l

In the drawing herewith I have used the reference numeral Il) to indicate generally the chimney on which my arrester'is employed.

I shall mention certain figures anddimensions as illustrativelet us assume that the chimney opening is 81/2 by 121/2". I provide therefor a box type arrester with side walls I I and end walls I2, all made of meshed wire. I have found that a reticulated material is apparently the best available. Extensive investigation demonstrates that the mesh should not be greater than 5/8 and that 1/2" is desirable. These meshes are..

critical. That is to say, the mesh should not be less than 1/2 because of the tendency to clog, nor greater than 5/8 because of the possibility of passing dangerous sparks.

The arrester has a top I3 of the same material, namely meshed wire, with a central opening I4 preferably of the same area as that of the chimney on which the arrester is to be used.

I nd that it is desirable to let the walls I2 and I I stand about 3" from the chimney opening. This is farther than common practice dictates. The edge of the material around the opening i4 is preferably downturned as at l5 for a short distance, perhaps 3A" to 1".

I hang an imperforate baille I6 centrally with relation to the side and end walls and about midway between the top and bottom of the arrester.

Investigation shows that the structure here shown has the best eilciency of all the arresters QC( have been able to test. The size of the mesh is such that it will not clog readily and yet will arrest the escape of sparks of dangerously large size. The provision of the hole in the top of the arrester eliminates the danger of clogging to the extent of substantially interfering with the draft. The baille is struck by a considerable proportion of soot particles and tends to break them up.

The baille also functions to abruptly change the direction of the flow of the gas stream and thus to draw the soot particles of the sparks out against the Wire mesh wall and to further cause them to Ybe broken up. The air stream is spread and distributed over a greater area and thereby serves to reduce its Velocity. This advantage would not be attained were it not for the relatively large size of the arrester with relation to the chimney opening. The baille partially breaks up the soot particles and also throws them out to the more slowly moving air and some of them are broken up against the wire mesh.

The vertical current bearing around the baille is slowed down greatly as it clears the baille edge.

The greater part of the glowing soot particles never get around the edge of the imperforate baille. In the comparatively few instances when they do pass around the baille there is no vertical air current of suilicient velocity to carry the sparks out.

I also nd that soot particles passing the edge `of the baille are projected into the upper corners of the spark arrester.

I have found that a similar baille made of screen mesh will not accomplish the purpose. There is enough vertical current in that case so that if any soot particles pass through the baille or around it, they may be carried out of the arrester.

Our tests show that an arrester of the kind shown here meets the requirements of a practical product.

The air velocity will vary, of course, depending on the kind of a chimney on which the arrester is used. However, I have found that with this type of an arrester the best results as to slowing down the air velocity above the baille, with little interference with the speed of the draft below the bafile, may be attained.

In making the tests to secure the proper arrangement, I have tested air velocities from almost nothing to a speed so violent that it passes that of any operating conditions. I have made tests with the arrester in still air and in side and end winds and with the breeze at 45 angles to the chimney. 'I'he arrester has been tested for clogging and sooting; various baille heights have been tried as well as various baille sizes.

The important thing is to utilize all four of the above expedients for preventing spark escape. Experiments lead to the conclusion that in attempting to utilize all four of such expedients the structural proportions above suggested should be used, that is to say, the arrester should be about 6" longer and 6" wider than the chimney opening and should fit symmetrically with such opening. The opening in the top of the arrester should be approximately the same as that in the chimney. The baille may safely be an inch shorter and an inch narrower than the chimney opening and should be located approximately mid-way between the top and the bottom -of the arrester. The height of the arrester may vary, of course, but for ordinary houses, is satisfactory. I have already mentioned the preferable size of the mesh to be used.

While small variations may be made in the size and proportions and arrangement of parts, approximately the proportions here set forth are desirable.

The advantage of a structure such as is here described is primarily in its effectiveness to prevent the escape of sparks and also in the fact that it does not unduly interfere with the normal operation of the chimney on which the apparatus is used.

I claim:

1. A spark arrester, adapted to be mounted on a chimney having a flue, having a wire mesh end and side walls and top, the top being open at its central part, an imperforate baille plate positioned centrally in the arrester about midway between the top and bottom thereof, the free area around the baille plate between it and the walls being substantially greater than that of the flue or the opening in the top and the area of the opening in the top being equal to or greater than the area of the plate.

2. A spark arrester having a Wire mesh end and side walls, and top, the top being open at its central part and having a down-turned flange around the opening, an imperforate baille plate positioned centrally in the arrester about midway between the top and bottom thereof, the free area around the baille plate between it and the walls being substantially greater than that of the opening in the top, and the area of the opening in the top being equal to or greater than the area of the plate.

HENRY GIESE. 

